The present invention relates to a hydraulic control system of an automatic transmission for an automotive vehicle, and in particular to a hydraulic control system for automotive vehicles which has a simplified structure, minimizes shift shock for improving shift responsiveness, and improves shift quality even in a driven state by a manual range shift and a power off state.
A conventional vehicle automatic transmission has a torque converter and a multiple stage transmission gear mechanism connected with the torque converter, and the transmission includes a hydraulically-actuated friction member for selecting one among a plurality of gear stages of the transmission gear mechanism in accordance with vehicle running conditions.
The hydraulic control system, which controls the operation of the friction members, selectively operates the friction members with hydraulic pressure generated by a hydraulic pump via a control valve. The hydraulic control system comprises a pressure control means for controlling hydraulic pressure generated by the hydraulic pump, a manual and automatic transmission control means that makes it possible to shift various transmission modes, a hydraulic control means for controlling the shift quality and responsiveness to form smooth transmission mode when shifting, a damper clutch control means for operating a damper clutch of a torque converter, a hydraulic pressure distribution means for supplying proper hydraulic pressure to each friction member.
The hydraulic control means regulates the supply line pressure exerting on the friction members, the torque converter supply pressure, and a solenoid valve supply pressure. These types of hydraulic pressure substantially affect on the shift quality.
Therefore, while shifting, it is preferable to supply controlled hydraulic pressure in order to operate friction members, and after this, to change the operating pressure of each friction member into drive pressure.
With this in mind, the present applicant disclosed a hydraulic control system which makes it possible to operate the friction members with drive pressure after operating the friction members with torque pressure in Korean Patent Application No. 94-37992.
However, when shifting manually and driven condition is at a power-off state, since there is no control process for these, shifting shock may occur.